Extrusion molding of inorganic masses, such as ceramic-forming materials has been performed by passing a green body or composition, which is obtained by mixing and kneading molding aids such as organic binders, surfactants, lubricants, and plasticizers with inorganic materials, particularly ceramic-forming materials, through dies having a desired shape into a sheet, a bar, a hollow tube, a rectangular column, a hollow rectangular column, or a honeycomb structure. In particular, the extrusion-molded body in the form of ceramic honeycombs has been in use as a carrier for exhaust gas cleaning catalysts, filters, and heat exchangers in the fields of automobiles and various industries.
U.S. Pat. No. 4,551,295 relates to the extrusion of a plastic ceramic batch into articles of widely-differing profiles and shapes such as, for example, dinnerware and electrical insulators, and especially the extrusion of thin-walled honeycomb structures from ceramic batches capable of flowing or plastically deforming under pressure during extrusion. The U.S. patent discusses that a methyl cellulose, such as METHOCEL™ A4M cellulose ether having a viscosity of 4000 mPa·s, measured as a 2 wt. % aqueous solution at 20° C. according to Ubbelohde has a low gelation temperature. According to FIG. 8 of the U.S. patent a sharp rise in extrusion pressure is observed when increasing the extrusion temperature in the range of 23-30° C. The U.S. patent discusses that such rise in extrusion pressure is not observed when using as a binder/plasticizer METHOCEL™ F4M cellulose ether which is commercially available from The Dow Chemical Company and has a viscosity of 4000 mPa·s. METHOCEL™ F4M cellulose ether has a methoxyl substitution of 27-30 weight percent and a hydroxypropoxyl substitution of 4.0-7.5 weight percent. The U.S. patent suggests using a hydroxypropyl cellulose having a viscosity of 25,000-100,000 mPa·s, measured as a 2 wt. % aqueous solution at 20° C. according to Ubbelohde to permit the use of working temperatures greater than 35° C. in a twin screw extrusion apparatus.
Japanese Patent publication JP4209747A discloses the use of methylhydroxypropyl cellulose in a ceramic extrusion process having a degree of substitution of methyl groups from 19-24% and hydroxypropyl groups from 10-16% and a aqueous viscosity, measured as 2% aqueous solution, from 65.000-120.000 cPs (mPa·s).
European patent application EP 2 157 064 A2 discloses that cellulose ethers are used in compositions for ceramic extrusion-molded bodies as an organic binder because of their excellent plasticity, water retention and thermal gelation characteristics. EP 2 157 064 A2 discusses that these cellulose ethers are disadvantageous in that they increase in frictional force with the die portion during extrusion molding and thus, the extrusion temperature rises owing to this frictional resistance. EP 2 157 064 A2 suggests solving this problem by additionally incorporating a styrenesulfonate in ceramic compositions comprising a ceramic material and a water-soluble cellulose ether for extrusion molding to enable extrusion molding at high temperatures and thus increasing the extrusion molding speed.
The International patent application WO2007/047103 relates to the use of an organic binder system which comprises an organic lubricant, such as a monocarboxylic acid like stearic acid, grafted to a cellulose ether binder, such as methylcellulose or hydroxypropyl methylcellulose like Methocel™ A4M and 20-333 and Methocel™ F240 available from The Dow Chemical Company.
Unfortunately, the use of styrenesulfonate or of cellulose ether binders to which a monocarboxylic acid has been grafted significantly increases the costs of compositions for extrusion-molded bodies.
Accordingly, it would be desirable to provide new compositions for extrusion-molded bodies which can be extruded at a reasonably low extrusion pressure. Technical and economic disadvantages of high extrusion pressures make operation of the extruders prematurely uneconomical due to high wear or high power costs.